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Common Questions About Heating, Ventilation and Cooling
What is an outdoor wood furnace?
Outdoor wood furnaces are the wood-fired furnaces which are typically housed in small, shedlike buildings. They are also known as outdoor wood furnace boilers or outdoor water stoves.
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An outdoor wood furnace usually consists of a large wood burning firebox surrounded by a water reservoir or ‘water jacket”. A tall chimney is used to vent the wood smoke generated. The burning of wood heats the water in the water reservoir, which then flows through underground pipes to a nearby home or building. Inside the building, the hot water warms the home with the help of radiators or a heat exchanger duct system.
The firebox of outdoor wood furnaces comes in various designs. It is usually made from stainless or carbon steel. Stainless steel fireboxes are considered better than the carbon steel fireboxes as the heat transfer efficiency is almost 3 times better with 16 gauge stainless steel than with 3/8" carbon steel. Moreover, stainless steel fireboxes also resist rusting and burnout that is common in standard carbon steel
The best feature of an outdoor furnace is that it can be located near the wood fuel source. Since the hot water is pumped to the house through insulated, underground piping, the furnace can be set up as much as 500 feet from the house. An outdoor wood furnace can heat a small-sized home for the entire season for the cost of one month’s electric heat bill. It also eliminates respiratory problems caused by indoor burning of wood and keeps the wood burning mess outside. All outdoor furnaces can be thermostatically controlled and usually work with any existing heating system.
Although outdoor wood furnaces have many advantages, they have some problems too. The wood smoke produced by the furnace causes smog over the entire neighborhood and makes these furnaces bones of contention between neighbors. These furnaces typically emit anywhere from 20 to 300 grams of particulate matter, or soot, per hour. Some health officials consider the outdoor wood furnaces the most polluting types of sources of heat and hot water even when burning clean, seasoned firewood. The owners of outdoor wood furnaces are sometimes advised to use their units more responsibly by limiting the operation to wintertime when neighbors are indoors. The moisture that causes smoke can be minimized by burning only dried wood. Installation of taller chimneys also helps in dispersing the smoke away from nearby homes.